BCA 20256462 - SHIELDING EFFECTIVENESS OF LASER-CUT WINDOWS IN RAIL VEHICLES (700 MHZ - 6 GHZ)
Repeaters have played a significant role in enhancing mobile coverage.
They work by capturing signals through an outdoor antenna, amplifying them, and then redistributing them indoors via cables or antennas. Despite their effectiveness, repeaters have drawbacks such as generating additional noise and the need for selective amplifiers to only boost specific frequencies, necessitating frequent updates for new frequency bands. MIMO technology implementation is complex, and these systems require ongoing monitoring and maintenance.
Additionally, when trains cross international borders, repeaters must be turned off, leading to a loss of mobile coverage for rail passengers.
An alternative method to improve mobile communications in train carriages involves reducing the car body's signal damping.
Using specially treated window panes is an effective approach. A laser-etched pattern in the metal layer of the windows, with structure sizes much smaller than the wavelength, is currently the preferred method. This creates a non-homogeneous metal layer perceived as an interrupted structure by the incoming wave, allowing the electric field to form between the elements.
The size of these structures significantly influences the damping of high-frequency bands.
The structure acts as a low pass filter, composed of the air's characteristic impedance and a capacitor, with the surface resistance of the layer in series. The width of the laser etching and the size of the tiles significantly affect the frequency response. The larger the ratio of metal to gap, the lower the 3dB cutoff frequency becomes.
At angles greater than 10° and up to 90°, there is a notable difference in reflection behavior between vertical and horizontal polarizations due to the Brewster angle.
This effect is a result of purely dielectric properties and is not influenced by laser design. Both polarizations only show similar dielectric behavior during orthogonal irradiation.
Therefore, measurements exclude angles beyond vertical incidence. To assess the polarization-specific impact of the laser design, both horizontal and vertical polarizations will be measured, and the specified limit values apply to both directions.
For practical use, the panes are fitted into a closed surface. At the testing station, varying disc masses and edge shapes can lead to different diffraction behaviors at the disc edges.
To minimize this effect, a minimum size of 110cm x 80cm (width x height) is mandated for the mesh.
Additionally, the disc is mounted in a standardized wall lined with absorber material in the measuring chamber.
The impact of the disc aperture is negated by a lee space measurement, ensuring that the disc size does not significantly affect the measurement outcome. However, it's important to note that the disc thickness and the gap between the two lenses are comparable to the wavelength of the upper spectrum. Consequently, a frequency response is anticipated, which will be factored into the decision-making criteria.
The frequency bands tested are as follows:
| Frequency |
Bands |
| 700 MHz |
Band 67, 68 |
| 800 MHz |
Band 20 |
| 900 MHz |
Band 8 |
| 1500 MHz |
Band 32, 51 |
| 1800 MHz |
Band 3 |
| 2100 MHz |
Band 1 |
| 2600 MHz |
Band 7 |
| 3500 MHz |
Band 42 |
| 3700 MHz |
Band 43 |
| 5000 MHz |
Band 46, 47 |
This standard is used for measuring radio wave transmission through a window, which is applicable to different types of vehicles, including trains, buses, and trams.
EMCTEST Technologies is a leading test laboratory in Italy and Europe for
electromagnetic shielding effectiveness testing. Thanks to advanced instrumentation and extensive experience in the field, we perform
measurements from 10 kHz to 110 GHz on materials and devices intended for
industrial, telecommunications, medical, military, automotive, railway, marine, aerospace, scientific, governmental, and civil applications.
Typical Test Frequencies
- Low frequency: 10 kHz, 100 kHz, 500 kHz, 1 MHz
- Mid frequency: 10 MHz, 30 MHz, 100 MHz, 433 MHz, 700 MHz, 800 MHz, 900 MHz
- High frequency (RF and microwave): 1 GHz, 1.5 GHz, 2.4 GHz (ISM band), 3 GHz, 5 GHz, 5.8 GHz, 6 GHz, 10 GHz
- Very high frequency: 17 GHz, 18 GHz, 24 GHz (ISM – Industrial, Scientific, and Medical bands), 26.5 GHz, 30 GHz, 35 GHz, 40 GHz, 50 GHz, 60 GHz (wireless communication and radar applications)
- Millimeter wave: 75 GHz, 77 GHz (automotive radar systems), 94 GHz, 100 GHz, 110 GHz
Our test laboratory is equipped to perform shielding effectiveness measurements up to 110 GHz.
You can read more on the home page. If you are looking for a laboratory to test your product, you are in the right place – feel free to contact us by email or phone.
Measurements are made according to customer specifications or in accordance with the main standards as below:
